// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef MEDIA_GPU_VP8_DECODER_H_
#define MEDIA_GPU_VP8_DECODER_H_

#include <stddef.h>
#include <stdint.h>

#include <memory>

#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "media/filters/vp8_parser.h"
#include "media/gpu/accelerated_video_decoder.h"
#include "media/gpu/vp8_picture.h"

namespace media {

// Clients of this class are expected to pass raw VP8 stream and are expected
// to provide an implementation of VP8Accelerator for offloading final steps
// of the decoding process.
//
// This class must be created, called and destroyed on a single thread, and
// does nothing internally on any other thread.
class MEDIA_GPU_EXPORT VP8Decoder : public AcceleratedVideoDecoder {
public:
    class MEDIA_GPU_EXPORT VP8Accelerator {
    public:
        VP8Accelerator();
        virtual ~VP8Accelerator();

        // Create a new VP8Picture that the decoder client can use for decoding
        // and pass back to this accelerator for decoding or reference.
        // When the picture is no longer needed by decoder, it will just drop
        // its reference to it, and it may do so at any time.
        // Note that this may return nullptr if accelerator is not able to provide
        // any new pictures at given time. The decoder is expected to handle
        // this situation as normal and return from Decode() with kRanOutOfSurfaces.
        virtual scoped_refptr<VP8Picture> CreateVP8Picture() = 0;

        // Submit decode for |pic|, taking as arguments |frame_hdr| with parsed
        // VP8 frame header information for current frame, and using |last_frame|,
        // |golden_frame| and |alt_frame| as references, as per VP8 specification.
        // Note that this runs the decode in hardware.
        // Return true if successful.
        virtual bool SubmitDecode(const scoped_refptr<VP8Picture>& pic,
            const Vp8FrameHeader* frame_hdr,
            const scoped_refptr<VP8Picture>& last_frame,
            const scoped_refptr<VP8Picture>& golden_frame,
            const scoped_refptr<VP8Picture>& alt_frame)
            = 0;

        // Schedule output (display) of |pic|. Note that returning from this
        // method does not mean that |pic| has already been outputted (displayed),
        // but guarantees that all pictures will be outputted in the same order
        // as this method was called for them. Decoder may drop its reference
        // to |pic| after calling this method.
        // Return true if successful.
        virtual bool OutputPicture(const scoped_refptr<VP8Picture>& pic) = 0;

    private:
        DISALLOW_COPY_AND_ASSIGN(VP8Accelerator);
    };

    VP8Decoder(VP8Accelerator* accelerator);
    ~VP8Decoder() override;

    // AcceleratedVideoDecoder implementation.
    bool Flush() override WARN_UNUSED_RESULT;
    void Reset() override;
    void SetStream(const uint8_t* ptr, size_t size) override;
    DecodeResult Decode() override WARN_UNUSED_RESULT;
    gfx::Size GetPicSize() const override;
    size_t GetRequiredNumOfPictures() const override;

private:
    bool DecodeAndOutputCurrentFrame();
    void RefreshReferenceFrames();

    enum State {
        kNeedStreamMetadata, // After initialization, need a keyframe.
        kDecoding, // Ready to decode from any point.
        kAfterReset, // After Reset(), need a resume point.
        kError, // Error in decode, can't continue.
    };

    State state_;

    Vp8Parser parser_;

    std::unique_ptr<Vp8FrameHeader> curr_frame_hdr_;
    scoped_refptr<VP8Picture> curr_pic_;
    scoped_refptr<VP8Picture> last_frame_;
    scoped_refptr<VP8Picture> golden_frame_;
    scoped_refptr<VP8Picture> alt_frame_;

    const uint8_t* curr_frame_start_;
    size_t frame_size_;

    gfx::Size pic_size_;
    int horizontal_scale_;
    int vertical_scale_;

    VP8Accelerator* accelerator_;

    DISALLOW_COPY_AND_ASSIGN(VP8Decoder);
};

} // namespace media

#endif // MEDIA_GPU_VP8_DECODER_H_
